Oxidizer and desiccator unit



Aug- 15, 1950 H. c. GERRlsH Er AL.

oxIDIzER AND nEsIccAToR UNIT Original Filed Oct. 25. 1943 grwa/wboa HAROLD C. GERRISH 8 J. LAWRENCE MEEM, JR.

Patentec ug. 15, 195,0

` UNITED STATES i TENT OFFICE OXIDIZER AND DESICCATORUNIT (Granted under the act `of March V3, 1883, as amended April 30, 1928; 370 0. G. 757) This invention relates in general to l'ow temperature oxidation of exhaust gasesxfiom internal combustion engines in connection with thermal-conductivity cells used in gas analysis.

As heretofore known, one type of gas analysis apparatus used for indicating the fuel-air ratio of the mixture fed to internal combustion engines over the iffnitable range of mixtures, is based upon the oxidation of the products of ineoinplete combustion by passing them through copper oxide heated to a high temperature, in the neighborhood of 900 to 1500 degrees Fahrenheit, and then determining the percentage of the several gas constituents in the resulting mixture, by means of the thermal conductivity cells, similar to those shown, for example, in prior Patent No. 2,298,288, issued October 13, 1942, to Gerrish and Reuter. This procedure requires the use of a furnace of some sort to attain these temperatures. In some cases, the furnace used is constituted by the exhaust stack of the engine, within which the copper oxide may attain the proper operating temperature. Such a procedure, however, makes servicing the oxidizer diicult whether the engine be in an airplane or other vehicle, in a laboratory, or elsewhere. r'he primary object of our invention is to` provide an oxidizing substance that will completely oxidize the hydrogen in the exhaust gases to water, the carbon monoxide to carbon dioxide, and the saturated and unsaturated hydrocarbons to carbon dioxide and Water while the exhaust gases are at room temperature or lower and without the use of a furnace or device for heating the oxidizing agent to so-me higher temperature.

A further object is to devise means whereby samples of the gases of combustion either from the exhaust stack of any cylinder of a multicylinder engine or from a collector ring into which all the individual cylinders discharge their exhaust gases, may be readily oxidized at a distance from the position or gas sampling without the difficulties necessarily encountered in inserting a high temperature oxidizerV in these gas sampling positions.

Further and more speciiic objects of this invention will become apparent from the following description thereof, having reference to the accompanying drawings, wherein:

Fig. 1 is an illustrative embodiment of our invention diagrammatically showing the gas circuit rom the position of sampling in the exhaust stack, through the desic'cator, the low temperature oxidizer, the thermal conductivity Ycells of Ythe analyzer or bridge circuit, and through the bubbler whereby the rate of gas ow is controlled;

Fig. 2 is a longitudinal section of one form of low temperature oxidizer unit, and

Fig. 3 is a section takenat 3-3 of Fig. 2.

It has been customary, in the type of analyzer referred to, to'pass the completely oxidized gases through a hot-wire instrument, whose operation depends upon the variation of the thermal conductivity of the oxidized gases of combustion with mixture strength, thereby to determine the mixture strength of the particular fuel-air mixture used in producingthe gases. The instrument is essentially a Wheatstone bridge whose resistance elements consists partially or totally of ilaments whose temperatures and therefore electrical resistances are inuenced by the thermal conductivity of the gases surrounding them,

`which conductivity is dependent on the percentage of CO2 in the gas, and this percentage is in turn dependent on the fuel-air mixture fed to the engine, provided all the carbon has been oxidized into CO2 and all the hydrogen into water.

For the oxidation of the exhaust gases, various oxidizers such as copper oxide, Hopcalite, etc., have been used, but the oxidation, to be effective, requires high temperatures.

It has been found that, by using oxidizing agents of the type to which our invention relates, the oxidation could be performed at room or lower temperatures, thus' overcoming the difliculties orf high temperature oxidation requirements.

The gas circuit used with these oxidizers, one form of which is shown in Fig. 1, is much simpler and easier to service with the oxidizing material than that used with any of the high temperature oxidizers. The oxidizers used in this invention are net merely catalysts but oxidizing agents. The oxygen for the reaction is supplied from the oxide mixtures themselves, and therefore it is not necessary to introduce some extraneous gas such as air to furnish the desired oxygen and thus vary the gas composition. We have found several substances which are well adapted to use in' our circuit. They are donned in a copending application Serial No. 507,388, filed October 23, 1943, of which the present application is a division, now abandoned.

These substances-V are various combinations of the' oxides of silver, manganese, copper cobalt,

3 tion is not to be limited to the specic mixtures and methods described.

Example 1.--A product consisting of the mixed oxides of silver, manganese and copper was prepared as follows: To a portion of 37 grams of silver nitrate in 2 litres of distilled water, 75 grams of aiinely powdered mixture of copper oxide and manganese dioxide known Icommercially as 'l-Iopcalite were added. Silver oxide was precipitated in the presence of the Hopcalite by the addition of sodium and potassium hydroxide. After settling, the material was washed by decantation six times with distilled water and liltered by suction.

lThe precipitate was dried for two hours at 75 C., pressed to a cake in a hydraulic pressand dried four hours longer at '75 C. After the second drying the cake was broken up and sieved to a lil-2i) mesh. These particles were placed in the oxidizer tube of the circuit of the fuel-air ratio indicator, with a layer of drying agent at either end and were then activated by the passage of a stream of dry air through the oxidizer at 150 C. for four hours.

Example 2.-A product consisting of the mixed oxides of silver and manganese was prepared as follows: 50 c c. of water were added to 136 grams of powdered potassium permanganate. 600 c c. of concentrated nitric acid were then slowly added but with vigorous stirring, the temperature of the reaction being kept below 60 C. The mixture was poured into a large bottle and washed by decantation until there was no further test for nitrates. Then it was washed several times with distilled'water and ltered by suction, then dried in an oven at 125 C. for ten to twelve hours. llhe resulting black powder was added to a solution of 37 grams of silver nitrate in 2 litres or" distilled water, and silver oxide was precipi?` tated with sodium or potassium hydroxide, the' resulting material after settling being washed and filtered and further treated as in Example 1.

Example 3.-A product consisting of the oxides of silver, cobalt and nickel was prepared as fol-` lows: 63 grams of nickelous nitrate and 65 grams cobaltous nitrate were dissolved in two gallons of water and the solution was saturated with chlorine. Concentrated sodium hydroxide was added to the solution while continuously bubbling chlorine therethrough precipitating cobaltic and niclielic oxides. After settling, the material was washed by decantation untilv there was no test for chloride or nitrate. It was then washed several times with distilled water and iiltered byrsuotion, then dried in an oven at 200 C. for twelve Y of the circuit shown in Fig. l, in which the exhaust from the engine is shown at I. The sampling conduit 2 extends into this exhaust and.. leads to a desiccator 3 from which the gas sam-`4 ple is passed through conduit t to the oxidizer tube 5, then through conduit 5 into the analyzer l, and from there through conduit 8 into the gas bubbler 9 from which it isA discharged into the` air through gas outlet i6. `The analyzer I may .be of any form such as shown for example in detail in the patent above referred to. The elec- Y trical connections I I for supplying the direct current potential to the analyzer and the connections I2 from the indicator I3 are passed through a cable I4 to the analyzer.

The details of the oxidizer tube may be seen in Figures 2 and 3. The body I5 of the oxidizer is cylindrical in shape and has 3 radial walls I6 as shown forming passages AB, BC, and AC. This construction permits a three-pass gas flow in the length of one pass and each pass utilizing the thermal conditions of the other passages to assist the completion of the reaction. Radial walls A and B are welded to the end plate at the gas entrance I'I whereas radial wall C is shortened here to allow passage of the gas from passage BC to passage AC. Radial walls A and C are welded to the end plate at the gas exit 'I8 whereas radial wall B is shortened to allow passage of the gas from passage AB to passage BC. The sample gases enter this oxidizer through inlet I1 and leave it by way of outlet I3. At the inlet and outlet is'` placed some desiccant material so as to keep the oxidant whichcompletely fills the rest of the oxidizer passages free from moisture. At the' inlet and outet is placed some desiccant material so as to keep the oxidant which fills the rest of the body of the oxidizer passage free from moisture.

Thus it may beseen that we have a simple form of analyzer system for determining the fuelair ratio of the mixture fed to any engine, to the exhaust of which this analyzer lis applied. rThis analyzer is easy to service because the oxidant used is of the type which operates at normal temperatures. It does not require any heating means such as previously used and therefore the oxidizer tube may be positioned so that it is easily accessible for replacement purposes. The oxidizer tube including the oxidant may be made replaceable so that as one oxidant is used up and becomes ineffective a new oxidizer tube with fresh oxidant all ready for operation may be readily substituted.

Obviously variousV modifications` may be made inY arrangement ofthe parts of our circuit, and different forms of the elements may be used without departing from the spirit of the invention, the scope of which is defined by the appended claim.

Thisinvention may be used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What we claim is:

A combined gas oxidizing and desiccating unit comprising a hollow cylindrical body closed at both ends,` a gas inlet port in one end, an outlet port in the other end, three longitudinally extending walls within said hollow cylindrical body in equi-angular spaced relationship to each other Aand radiating Ifrom the longitudinal axis to the ing with the passageway formed by the said rst' and second walls and said cylindricalV body and the saidf outlet port communicating withthe passageway formed by said first and third walls and said cylindrical body whereby a continuousl three pass passageway is lformed between said` inlet andv outlet ports, said three pass passageway adapted to be substantially filled with an oxidizing agent.

HAROLD C. GERRISH. JAMES LAWRENCE MEEM, JR.

REFERENCES CITED Number UNITED STATES PATENTS Name Date Katz Mar. 30, 1926 Number 6 Name Date Schmidt;l June 26, 1928 Pick Jan. 21, 1930 Gilliland et al. Feb. 26, 1935 Cambron et al May 28, 1935 Howe June 18, 1935 Willenborg June 2, 1936 Moore et al June 11, 1940 Payne June 10, 1941 Gerrish et, al. Oct. 13, 1942 Hulsberg Apr. 6, 1943 Sanderson Mar. 28, 1944 

